title: Frizzled-8 receptor is activated by the Wnt-2 ligand in non-small cell lung cancer.
abstract: BACKGROUND
  Wnt-2 plays an oncogenic role in cancer, but which Frizzled receptor(s) mediates the Wnt-2 signaling pathway in lung cancer remains unclear. We sought to (1) identify and evaluate the activation of Wnt-2 signaling through Frizzled-8 in non-small cell lung cancer, and (2) test whether a novel expression construct dominant negative Wnt-2 (dnhWnt-2) reduces tumor growth in a colony formation assay and in a xenograft mouse model.
  
  
  METHODS
  Semi-quantitative RT-PCR was used to identify the expression of Wnt-2 and Frizzled-8 in 50 lung cancer tissues from patients. The TCF reporter assay (TOP/FOP) was used to detect the activation of the Wnt canonical pathway in vitro. A novel dnhWnt-2 construct was designed and used to inhibit activation of Wnt-2 signaling through Frizzled-8 in 293T, 293, A549 and A427 cells and in a xenograft mouse model. Statistical comparisons were made using Student's t-test.
  
  
  RESULTS
  Among the 50 lung cancer samples, we identified a 91% correlation between the transcriptional increase of Wnt-2 and Frizzled-8 (p<0.05). The Wnt canonical pathway was activated when both Wnt-2 and Frizzled-8 were co-expressed in 293T, 293, A549 and A427 cells. The dnhWnt-2 construct we used inhibited the activation of Wnt-2 signaling in 293T, 293, A549 and A427 cells, and reduced the colony formation of NSCLC cells when β-catenin was present (p<0.05). Inhibition of Wnt-2 activation by the dnhWnt-2 construct further reduced the size and mass of tumors in the xenograft mouse model (p<0.05). The inhibition also decreased the expression of target genes of Wnt signaling in these tumors.
  
  
  CONCLUSIONS
  We demonstrated an activation of Wnt-2 signaling via the Frizzled-8 receptor in NSCLC cells. A novel dnhWnt-2 construct significantly inhibits Wnt-2 signaling, reduces colony formation of NSCLC cells in vitro and tumor growth in a xenograft mouse model. The dnhWnt-2 construct may provide a new therapeutic avenue for targeting the Wnt pathway in lung cancer.
authors.affiliation: Department of Surgery, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA 94115, USA.
authors.forename: Dawn T
authors.initials: DT
authors.lastname: Bravo
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Yang
authors.forename: Kristopher
authors.initials: K
authors.lastname: Kuchenbecker
authors.forename: Ming-Szu
authors.initials: MS
authors.lastname: Hung
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Xu
authors.forename: David M
authors.initials: DM
authors.lastname: Jablons
authors.forename: Liang
authors.initials: L
authors.lastname: You
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D051157:Frizzled Receptors / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008175:Lung Neoplasms / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D051154:Wnt2 Protein / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D051157:Frizzled Receptors; D008024:Ligands; D051154:Wnt2 Protein